PURPOSE: To secure sufficiently the required flow rate without waste by forming electrolytic chambers on the anode side and the cathode side by means of a double diaphragm for dividing, supplying raw water between the double diaphragms and actuating the hydraulic pressure between the double diaphragms in the state of being higher than the hydraulic pressure of respective electrolytic chambers.

CONSTITUTION: An anode side electrolytic chamber 3 and a cathode side electrolytic chamber 4 are formed by dividing the inside of an electroytic container 1 by means of double diaphragms 2 in a double diaphragm electrolytic device, and raw water is supplied between the double diaphragms 2 to actuate the hydraulic pressure between the double diaphragms 2 in the state that the above-said hydraulic pressure is higher than the hydraulic pressure in respective electrolytic chambers 3 and 4. When water is applied from the inner side of the diaphragms 2 formed double, the generation of the short pass is controlled by the internal pressure of the diaphragms 2 even when the pressure variation is generated by the flow rate variation in the two electrolytic chambers 3 and 4. The flow rate ratio of electrolytic water, therefore, can be increased and waste drain is decreased to secure sufficiently the required flow rate without waste.